A semiconductor device includes a cell source line which supplies a voltage to logic circuits, a capacity source line which supplies a voltage to the cell source line, a control circuit source line, switches by which the cell source line is isolated from or connected to the capacity source line and the control circuit source line, and buffer circuits which drive signals which control the switches, respectively. When the system is activated, a potential is applied to the capacity source line for charging, after which the cell-to-capacity switch is turned on. Then, a voltage is applied to the cell source line, which allows a steep rise in voltage at the cell source line. As a result, charging time is reduced and flow-through current which flows through transistors constituting the logic circuit can be reduced as well.
